Traditionally, operating of switching devices is performed by use of spring mechanisms with enough energy to obtain opening and closing of switching device. In a classical spring operating mechanism OPEN and CLOSE signals are the only real-time signals present Spring mechanisms do not perform exactly the same from one opening/closing operation to another. Therefore, the time delay from order to completed operation is not constant. It is not possible to control and regulate the motion and position of the contact parts in an exact way. Communication in a system with a traditional spring switching device includes tripping coils.
In a switching device using a spring mechanism, the spring will apply the same force on the contact part at every operation, so it has to be designed to operate as if a worse case current were to be interrupted at every operation. In a spring mechanism, the time delay is not constant. In a spring mechanism system external measurement equipment must be connected to collect information regarding the operation of spring mechanism, and must remain connected during all switching device operation s from which one wants to obtain information. In practice this means that to test a switching device, it must be taken out of service, measuring equipment must be connected and some operations must be performed.
In order to overcome the drawbacks related to a spring operated switching device it has been suggested to use an electric motor for operating the mobile contact part. WO 00/136621 discloses an example of this type of switching device.
According to WO 00/136621 the movement of the mobile contact part is controlled. A control unit receives input information, which information includes information about the network condition, the movement of the mobile contact part, the movement of the rotor of the electric motor and/or instructions for an operator. Based on this information the control unit controls the motor movement by controlling the current supplied thereto. The movement follows a motion profile stored in the control unit and the movement is adapted to the feedback information from the input
This known device represents an important improvement in relation to a spring operated switching device since it offers some degree of control of the motion. Furthermore operation and control of the switching device requires less local activity of service persons than traditionally operated switching devices.
Since this known device requires that the switching device has to be equipped with complicated software in order to control the motion of the mobile contact part to full extent, it follows that tests, adjustments and similar maintenance actions require local activity by service personal. Also supervising the switching device and adapting it to changing conditions has to be locally administered.
WO 00/28565 discloses a circuit breaker that in certain aspects can be remotely actuated. This known device has a receiver arranged to receive remotely transmitted control signals. These controls, however, mainly have the function of an on/off-control. The disclosure leaves unclear whether the control includes any possibility for more sophisticated control. Furthermore it is clear that there is no means allowing any feedback regarding the operation of the circuit breaker. This device therefore is not suitable for eliminating or reducing the need for local activities of the kind discussed above.